fix(components): [tree] add missing type reject for LoadFunction

[kaedeair]

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修复了Tree组件懒加载方法中reject函数的类型缺失问题 #16099

[pull-request-triage]

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[github-actions]

[github-actions]

Hello @kaedeair, thank you for contributing to element-plus, please see our guideline to see how to make contribution

[kaedeair]

It causes build fail using typescript while linting strict on
Playground

Type '(node: Node, resovle: (data: Tree[]) => void, reject: () => void) => void' is not assignable to type 'LoadFunction'. Target signature provides too few arguments. Expected 3 or more, but got 2.ts(2322)

[btea]

Thanks!

[github-actions]

🧪 Playground Preview: https://element-plus.run/?pr=16990
Please comment the example via this playground if needed.